Victor K. Tripp

Design of multioctave spiral-mode microstrip antennas

The design of spiral-mode microstrip antennas with a bandwidth of 6:1 is demonstrated. The antenna has a small dissipative loss due to a resistive loading outside its active region. As a specific measure of bandwidth at microwave frequencies, the spiral-mode microstrip antenna gain is higher than that of the conventional loaded-cavity spiral over a 5:1 and if the spacing d between the microstrip and the ground plane is 0.25 in. or larger over the 2-12 GHz range. Cursory efficiency calculations show consistent improvement over a loaded-cavity spiral. A study of ground plane spacing showed that the antenna gain remains above the conventional spiral gain as d is reduced until it is as small as 0.1 in. >

Conformal low-profile multifunction antennas

The spiral-mode microstrip (SMM) antenna of Wang and Tripp (see IEEE Trans. Ant. Prop., p.332-335, March 1991) has two characteristics which make it uniquely suitable as a multifunction antenna: (1) multioctave frequency bandwidth, (2) radiation pattern diversity. In addition, the SMM antenna is conformable, low-profile, and includes a conducting ground plane; therefore, it can be readily mounted on the surface of an aircraft, missile, or other vehicle. The development of a multifunction SMM antenna for aircraft communications in the 0.2 to 1.6 GHz range is discussed.

The magnetically coated conducting surface as a dual conductor and its application to antennas and microwaves

An electric conducting surface coated with a thin, lossy magnetic layer has been both theoretically and experimentally observed to be equivalent to a surface that is conducting to both electric and magnetic fields of plane waves at near-grazing incidence angles. This dual conductivity phenomenon has been utilized to design horn antennas for desired performance characteristics such as symmetric beams, low sidelobes, and low cross polarization. The effects of this surface are in many ways similar to those of the corrugated conducting surface. However, this coated surface appears to have a broader spectrum of applications in other antennas and microwave devices because of its apparent dual (electric and magnetic) conductivity. >

Design and performance of the magnetic hybrid-mode horn

Design techniques are presented for a class of circular magnetic hybrid-mode (MHM) horns together with experimental results. In comparison with earlier techniques, this design method is simpler and more amenable to physical interpretation. The horns designed exhibit performance comparable to that of the corrugated horn except that they have an ohmic loss of 0.8 to 2.7 dB. However, it appears feasible to reduce the gain loss to less than 1 dB. >

Development of a novel faceted, conformal, slotted-waveguide subarray for sensor applications with full 360° azimuth tracking capabilities

This paper describes the design and implementation of a conformal subarray antenna that was developed as part of a larger circular array which is intended to provide full 360deg azimuth coverage for a sensing system operating from 16 - 16.6 GHz. Despite the fact that several technologies from prior art were incorporated into the design of the presented center-fed, narrow-wall slotted waveguide array, the innovative character of this approach lies in the development of a faceted conformal waveguide subarray and its use with neighboring similar arrays to provide azimuth angular tracking information. The measured reflection coefficient and radiation patterns of two fabricated prototypes demonstrate good agreement with those predicted by FEM simulations.

A new density tapering method based on radial warping

We examine element placement in a planar array when the minimum spacing is greater than a wavelength. We propose a new convenient density tapering method using a radial warping function based on the prototype taper, discuss its relation to other deterministic density tapering methods, including statistical density tapering, and demonstrate that it yields no grating lobes.

A new tapered double balun for spiral-mode 2

The tapered balun (J.W. Duncan and V.P. Minerva, 1960) is an excellent feed for very broadband, balanced antennas, such as spirals and sinuous antennas. Its bandwidth is limited only at the low-frequency end, which can be made arbitrarily low by making the taper longer. Furthermore, it can be easily designed and fabricated in an inexpensive printed circuit medium. A four-arm spiral antenna that operates only in mode 2 (R.G. Corzine and J.A. Mosko, 1990) really has only two electrical terminals since opposite arms theoretically can be connected together. However, practically, it is not obvious how to achieve this connection in a rugged and inexpensive way. A clever tapered coplanar-line balun has been reported (E. Gschwendtner, 1999) but a cavity will interfere with it, and the authors do not discuss how to make it balanced at the feed point. This paper describes a new tapered double balun that solves these issues and provides an improved technique to excite mode 2 for four-arm spirals.

Implementation of blinds for cross-polarization reduction on a conformal slotted-waveguide subarray

This paper describes the design and implementation of blinds whose purpose is to reduce cross-polarized radiation from slotted waveguide subarray antenna. The conformal, faceted subarray was developed as part of a larger circular array which is intended to provide full 360deg azimuth coverage for a sensing system operating from 16-16.6 GHz. The blinds were added to the waveguide to reduce the radiated cross-polarization levels. This paper presents the design and physical implementation of the blinds. A comparison is presented between measured and FEM-modeled directivity patterns demonstrating the effectiveness of the technique.

Multiband antenna for airborne satellite communications

Satellite broadcasting of weather information promises to provide an economical method of improving aviation safety for commercial and general aviation transportation. The paper presents an airborne antenna developed to receive satellite weather information around the world. To accomplish this, the antenna supports three separate frequency bands and dual senses of polarization. Method of moments (MoM) and finite element method (FEM) simulations were employed in the development of the antenna. Details of the prototype antenna and its performance evaluation are presented.

Frequency-independent geometry for a two-dimensional phased array

This paper presents a log-periodic phased-array (LPPA) geometry that does not attempt to simulate the conventional periodic grid. It is a very simple geometry that provides arbitrarily large bandwidth and frequency-independent performance without grating lobes. The array can be fed and scanned like conventional arrays. Since the array is sparse, the sidelobe levels may be higher than those of conventional arrays, but broadband, closely packed elements can provide very reasonable sidelobe levels.